Our major objective continue to be the development of a clinically reliable system for detection, evaluation and monitoring of bladder cancer by flow cytometer (FCM). During this last period conventional bladder irrigation FCM, using acridine orange (AO) staining, compared with voided urine cytology and bladder wash cytology, demonstrated significantly higher sensitivity for FCM. Prior studies indicated specificity above 90%. Additional studies of FCM as a means of monitoring disease in patients undergoing conservative intravesical drug or immunotherapy now will be pursued; and technique modification to facilitate use of FCM on mail-in fixed specimens, and possibly on voided urine. However, the major effort now is directed toward providing information on the biologic behavior or characteristics of bladder tumor, when it is present, beyond what is possible by simple cytologic or histologic light microscopy. To do this, several different approaches will be taken, making use of the large volume of clinical material available at this institution and the strengths of our own team as well as the tumor immunologists working with Dr. Lloyd Old, with whom we are collaborating. Specifically, these include: 1) measuring true tumor proliferative rate, as determined by BrdUrd uptake in exfoliated cells incubated in vitro after irrigation or in vivo by instillation of BrdUrd into the bladder. 2) FCM evaluation of monoclonal antibodies (MoAbs) to human bladder tumor associated antigens that discriminate low grade from high grade tumors. (MoAbs Om5 and T43). 3) monoclonal antibodies to blood group related antigens and cytoskeletal proteins. 4) nuclear chromatin structural changes in situ, 5) FCM of short term cultures of bladder tumor cells from irrigation specimens. These goals will require multi-parameter measurements of DNA, RNA and/or one or two antigens, for which dual laser flow cytometry and new methods of cell preparation and staining are required. Absolute measurements of cytoplasmic components, which are inaccurate for broken cells that have lost cytoplasm during exfoliation, can be corrected by using ratios of two cytoplasmic components as the basis for correlation with clinical, cystoscopic and pathologic findings in the studies proposed. With these new FCM techniques, the urologist and oncologist will be provided very powerful new tools that not only identify and quantify the tumor cells present but yield information on functional attributes and biologic behavior that will play an increasing role in the management of carcinoma and precancerous lesions of the bladder.